diff --git a/frontend/src/hooks/useSleepSession.ts b/frontend/src/hooks/useSleepSession.ts
index a64c7d3..b910402 100644
--- a/frontend/src/hooks/useSleepSession.ts
+++ b/frontend/src/hooks/useSleepSession.ts
@@ -1,6 +1,6 @@
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
 import { fetchActiveSession, createSession, endSession, fetchSessions, deleteSession, updateSession } from '../api/client';
-import type { SleepSessionRead } from '../types';
+import type { SleepSessionRead, SleepSessionCreate } from '../types';
 
 export function useSleepSession() {
   const queryClient = useQueryClient();
@@ -12,7 +12,7 @@ export function useSleepSession() {
   });
 
   const createMutation = useMutation({
-    mutationFn: (args) => createSession(args),
+    mutationFn: (args: SleepSessionCreate) => createSession(args),
     onSuccess: () => {
       queryClient.invalidateQueries({ queryKey: ['activeSession'] });
       queryClient.invalidateQueries({ queryKey: ['sessions'] });
@@ -20,7 +20,7 @@ export function useSleepSession() {
   });
 
   const endMutation = useMutation({
-    mutationFn: (args) => endSession(args.sessionId, { end_time: args.endTime }),
+    mutationFn: (args: { sessionId: number; endTime: string }) => endSession(args.sessionId, { end_time: args.endTime }),
     onSuccess: () => {
       queryClient.invalidateQueries({ queryKey: ['activeSession'] });
       queryClient.invalidateQueries({ queryKey: ['sessions'] });
@@ -47,7 +47,7 @@ export function useSessions() {
   });
 
   const deleteMutation = useMutation({
-    mutationFn: (id) => deleteSession(id),
+    mutationFn: (id: number) => deleteSession(id),
     onSuccess: () => {
       queryClient.invalidateQueries({ queryKey: ['sessions'] });
     },